Sentences with phrase «glaciation about»

During a period of glaciation about 660,000 years ago, Himalayan brown bears were one of the first groups to branch off and become distinct from other brown bears, the data suggest.

Not exact matches

In particular, the 1.55 meters of bedrock at the core's base revealed much about the island's history of glaciation, Schaefer says, in atoms that chronicle exposure to the elements.

Nevertheless, during a 10 - million - year - period that started about 455 million years ago, Earth experienced two major glaciations.

Climate models suggest that widespread glaciations couldn't take place at that time unless CO2 levels dropped to about eight times what they are at present, says Tim Lenton, an earth scientist at the University of Exeter in the United Kingdom.

«In addition, this early phase of evolutionary divergence appears to have preceded the extreme climate changes that led to Snowball Earth, a period marked by severe long - term global glaciation that lasted from about 720 to 635 million years ago,» Dohrmann says.

From the onset of northern - hemisphere glaciation (about 3 million years ago) to the «mid-Pleistocene transition» (about 800,000 years ago), glacial advance and retreat follows a strong 41,000 - year cycle, which has led to its being called «the 41 ky world» (Raymo & Nisancioglu 2003, Paleoceanography, 18, 1011).

[10] Earlier still, a 200 - million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 million years ago, by a colossal volcanic outgassing which raised the CO2 concentration of the atmosphere abruptly to 12 percent, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day.

During the most recent North American glaciation, during the latter part of the Wisconsin Stage (26,000 to 13,300 years ago), ice sheets extended to about 45 degrees north latitude.

During glaciation, water was taken from the oceans to form the ice at high latitudes, thus global sea level drops by about 120 meters, exposing the continental shelves and forming land - bridges between land - masses for animals to migrate.

This caused weathering to decrease by about 4 times globally, allowing CO2 and temperatures to recover, terminating the glaciation,» Pogge von Strandmann said.

There seems to be little contention about glaciation and its impact on possible migration, or about the microclimatic variations along the Pacific coast of North America.

How about xkcd's «A Timeline of Earth's Average Temperature since the Last Ice Age Glaciation: When people say «The climate has changed before» these are the kinds of changes they are talking about» https://xkcd.com/1732/

First, there is very little in the way of archaeological data about cvilzations during the transition from the last glaciation to the Holocene.

To think we understand a lot about of Ice Ages when we can only guess whether the next glaciation begins in 20K or 50K years seems self - contradictory on the face of it.

Since you elected not to address the issue of models capability to represent critically - important glaciation - deglaciation episodes, now I have developed an impression that certain climate scentists have to learn a lot more about possibilities that are hidden in behavior of a large and complex dynamical system.

Humanity «rose» from the onset of this current period of recurring glaciations ~ 3 Million years ago, and from the above site (**): -[«During the last warm spell, 125,000 years ago, the seas were about 18 feet higher than they are today.

We have stil l about 30 or 40K years before the next glaciation absent anthropogenic disturbances.

Such states may have prevailed in the distant past, but there is nothing about the current Holocene climate to suggest that more than a single equilibrium is within range — we are not close to a new glaciation nor a new «hothouse climate» (although the latter might become possible if continued greenhouse gas emissions were to remain unmitigated for a prolonged interval).

on top of the slow slide towards the next glaciation, due to the current state of the Milankovitch cycles, plus there was also concern about a «nuclear winter» (a lot of dust thrown up) should a war break out adding a lot to the several cooling elements.

Glaciation lasts about 100,000 yrs while interglacial warmth is a 15,000 - 20,000 year episode.

During the past 20,000 years (the Holocene), since the end of the last glaciation, sea level has risen a total of about 120 m above modern shorelines, initially at a rate many times faster than observed anywhere today.

There is, however, still an ongoing and partly controversial debate about the timing and extent of maximum glaciations.

If he's worried about ice ages, perhaps he should ponder the selfishness of squandering what could have been a useful geoengineering resource to future generations faced with an imminent glaciation; carefully burning fossil fuels to enhance the greenhouse effect just enough to maintain temperatures in the face of declining northern - hemisphere insolation due to the Milankovich cycles may well be the most cost - effective method for them to do so, if those resources are still around at the time.

I just found this info on the Gaskiers Glaciation and the 90 km diameter meteorite impact at around the same time (about 590 Mya)(I am interested in this because I worked in the area in 1967 - 68).

At the height of the last glaciation the sea level was about 120 metres lower than it is today.

Today Earth is a pretty temperate place, but about 700 million years ago ice covered the planet from pole to pole, in an extreme glaciation period often called «Snowball Earth.»

Given that a CO2 doubling or halving is equivalent to a 2 % change in solar irradiance [66] and the estimate that solar irradiance was approximately 6 % lower 600 Ma at the most recent snowball Earth occurrence [113], figure 7 implies that about 300 ppm CO2 or less was sufficiently small to initiate glaciation at that time.

Subsequently, large Northern Hemisphere glaciations began to occur when pCO2 dropped below about 300 ppm in the middle Pliocene.

The Cenozoic record also reveals the amplification of climate change that occurs with growth or decay of ice sheets, as is apparent at about 34 Myr BP when the Earth became cool enough for large - scale glaciation of Antarctica and in the most recent 3 — 5 Myr with the growth of Northern Hemisphere ice sheets.

Then, around 1 million years ago, glaciations got longer, with cycles lasting for about 100,000 years.

Fear Ice, Brandon; set about estimating the best manner and timing to release AnthroCO2 to ameliorate glaciation.

The predominance of landmasses in the northern hemisphere causes glaciations to predominate over interglacials by about 9 to 1 with a full cycle every 100, 000 years helped along by the orbital changes of the Milankovitch cycles that affect the pattern of insolation on those shifting cloud masses.

What the clueless folks you are trying to reach actually need to know is that each decade is warmer than the last, at a rate near 2 degrees Celsius per century, which might well increase, and for comparison the difference between Ice Age glaciation and the climate we like is about 6 degrees Celsius.

In my search to be informed about all this global warming and co2 concern I found the Orbital Variations in connection with the Stages of Glaciation very interesting.

The warm periods between glaciations last about 10,000 years.

[65] Earlier still, a 200 - million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 Ma, by a colossal volcanic outgassing that raised the CO2 concentration of the atmosphere abruptly to 12 %, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day.

For Stage 11, these conceptual models show that the deglaciation was triggered by the insolation maximum at about 427 ka, but that the next insolation minimum was not sufficiently low to start another glaciation.

And what finally caused Northern Hemispheric glaciation at about the same time — but nearly 2 million years after the Isthmus of Panama formed?

for long enough that we should be concerned about runaway glaciation.

Indeed, they note that about 800,000 years ago, orbital alignments were similar but carbon dioxide concentrations were around 240 parts per million, and glaciation did indeed occur.